Periodic-wave disc brake rotor

ABSTRACT

A disc brake rotor includes an annular portion having a first surface and a second surface in opposition to the first surface. The first surface and second surface traverse a periodic wave. An inner radial edge of the annular portion traverses an inner periodic wave and an outer radial edge of the annular portion traverses an outer periodic wave. A pattern and a period are the same for the periodic wave, the inner periodic wave, and the outer periodic wave. Thermal radiation elements are coupled to portions of at least one of the inner radial edge and the outer radial edge.

ORIGIN OF THE INVENTION

The invention described herein was made by an employee of the UnitedStates Government and may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefore.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to disc brake rotors. More specifically, theinvention is disc brake rotor whose braking surfaces traverse a periodicwave.

2. Description of the Related Art

Disc brake rotors include opposing axial surfaces that are engaged by abrake caliper during braking as is well known in the art. A disc brakerotor can be mounted at a wheel's hub or the perimeter of a wheel. Bothtypes generate substantial heat during a braking operation that requiresdissipation for brake efficiency and longevity. In addition, the weightof a perimeter-mounted disc brake rotor can be substantially more than ahub-mounted disc brake rotor since a perimeter disc brake rotor has amuch larger diameter. The increased weight requires additional energy torotate a wheel having a perimeter disc brake rotor coupled thereto.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide discbrake rotor having improved heat dissipation.

Another object of the present invention is to provide a disc brake rotorthat includes weight reducing features.

Still another object of the present invention is to provide a perimeterbrake rotor having heat dissipation and weight reducing features.

Other objects and advantages of the present invention will become moreobvious hereinafter in the specification and drawings.

In accordance with the present invention, a disc brake rotor includes anannular portion having a first surface and a second surface inopposition to the first surface. The annular portion has an axialthickness T between the first surface and the second surface. The firstsurface and the second surface traverse a periodic wave wherein an innerradial edge of the annular portion traverses an inner periodic wave andan outer radial edge of the annular portion traverses an outer periodicwave. A pattern and a period are the same for the periodic wave, theinner periodic wave, and the outer periodic wave. Thermal radiationelements are coupled to portions of at least one of the inner radialedge and the outer radial edge.

BRIEF DESCRIPTION OF THE DRAWING(S)

Other objects, features and advantages of the present invention willbecome apparent upon reference to the following description of thepreferred embodiments and to the drawings, wherein correspondingreference characters indicate corresponding parts throughout the severalviews of the drawings and wherein:

FIG. 1 is an axial end view of a periodic-wave disc brake rotor inaccordance with an embodiment of the present invention;

FIG. 2 is a radial cross-section of the disc brake rotor taken alongline 2-2 in FIG. 1;

FIG. 3 is a radial cross-section of the disc brake rotor take along line3-3 in FIG. 1;

FIG. 4 is an axial end view of a portion of a periodic-wave disc brakerotor in accordance with another embodiment of the present invention;

FIG. 5 is an axial end view of a portion of a periodic-wave disc brakerotor in accordance with still another embodiment of the presentinvention;

FIG. 6 is an axial end view of a circular dimpled periodic-wave discbrake rotor in accordance with another embodiment of the presentinvention;

FIG. 7 is a radial cross-section of the disc brake rotor take along line7-7 in FIG. 6;

FIG. 8 is a radial cross-section of the disc brake rotor take along line8-8 in FIG. 6;

FIG. 9 is an axial end view of elongate-dimpled periodic-wave disc brakerotor in accordance with another embodiment of the present invention;

FIG. 10 is a cross-section of the disc brake rotor that spans the widthof an elongate dimpled region of the rotor take along line 10-10 in FIG.9;

FIG. 11 is an isolated cross-sectional view of a dimpled region of adisc brake rotor illustrating the convective and conductive coolingeffects provided thereby; and

FIG. 12 is an isolated cross-sectional view of a dimpled region of adisc brake rotor where the surface of the dimple has been coated with ahigh thermal emissivity material in accordance with another embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, simultaneous reference will be made toFIGS. 1-3 where a disk brake rotor in accordance with an embodiment ofthe present invention is shown and is referenced generally by numeral 10in FIG. 1. The novel features of the present invention that will bedescribed for the non-limiting exemplary embodiments thereof can beapplied to both hub-mounted and perimeter-mounted disc brake rotors. Byway of non-limiting illustrative examples, the present invention will beexplained herein for perimeter disc brake rotors. For simplicity ofillustration and clarity of description, features of the presentinvention that facilitate its coupling to a wheel (not shown) or hubhave been omitted as a variety of wheel (or hub) attachment schemesknown in the art could be used without departing from the scope of thepresent invention.

FIG. 1 presents an axial end view of disc brake rotor 10 where the axisof rotation of rotor 10 is indicated by numeral 11. Rotor 10 includes anannular portion 20 that defines the braking surfaces of rotor 10 and aplurality of thermal radiation elements 30 coupled to annular portion20. Annular portion 20 and thermal radiation elements 30 can be made asan integral or assembled structure without departing from the scope ofthe preset invention. Materials used to construct rotor 12 can includeone or more of metals, composites, etc., known in the art of brake rotorconstruction without departing from the scope of the present invention.

Annular portion 20 has two axial opposing surfaces, i.e., surface 22visible in FIGS. 1-3 and surface 24 visible only in FIGS. 2 and 3.Opposing surfaces 22 and 24 will be engaged by a brake caliper (notshown) during a braking operation as would be understood by one ofordinary skill in the art. In accordance with the present invention,each of opposing surfaces 22 and 24 traverses a periodic wave aroundannular portion 20. In the illustrated embodiment, the periodic wave isa trapezoidal wave. However, the present invention is not so limited asthe periodic wave presented by annular portion 20 could be triangular asshown in FIG. 4, sinusoidal as shown in FIG. 5, or any other periodicwave shape without departing from the scope of the present invention.

Referring again to FIGS. 1-3, an inner radial edge 26 and outer radialedge 28 of annular portion 20 also traverses a periodic wave. Morespecifically, inner radial edge 26 and outer radial edge 28 traverseperiodic waves that have the same pattern and period as the periodicwave defining opposing surfaces 22 and 24. One or both of radial edges26 and 28 can have thermal radiations elements 30 coupled to portionsthereof. For example, in the illustrated embodiment, elements 30 arecoupled to both radial edges 26 and 28 and extend between adjacentcrests of the periodic wave defining edges 26 and 28. Elements 30 serveas radiators of heat generated at annular portion 20 during a brakingoperation. To reduce the weight of rotor 10 while still providing goodthermal radiation, a ratio of t/T of 0.1 to 0.3 is maintained where T isthe axial thickness of annular portion 20 between opposing surfaces 22and 24, and t in the axial thickness of thermal radiation elements 30 asshown in FIGS. 2 and 3.

The present invention can be further adapted to provide additional heatdissipation and weight reducing features. For example, and withsimultaneous reference to FIGS. 6-8, a disc brake rotor in accordancewith another embodiment is shown and is referenced generally by numeral40 in FIG. 6. Similar to rotor 10 described above, FIG. 6 presents anaxial end view of disc brake rotor 40 having an axis of rotationindicated by numeral 41. Rotor 40 includes an annular portion 50defining opposing braking surfaces 52 and 54, and thermal radiationelements 60. Annular portion 50 traverses a triangular wave such that aninner radial edge 56 and outer radial edge 58 also traverse a triangularwave having the same pattern and period as the triangular wave definingopposing surfaces 52 and 54. Thermal radiation elements 60 can becoupled to one or both (as shown) of radial edges 56 and 58 betweenadjacent crests of the edges defining the periodic wave. Similar torotor 10, the weight of rotor 40 is reduced by maintaining a ratio oft/T between 0.1 and 0.3 where T is the axial thickness of annularportion 50 between opposing surfaces 52 and 54, and t is the axialthickness of elements 60 as shown in FIGS. 7 and 8.

Rotor 40 additionally includes dimples 62 in one or both (as shown) ofopposing surfaces 52 and 54. As will be explained further below, dimples62 enhance convective, radiation, and conduction cooling effects ofrotor 40. In the illustrated example, dimples 62 are circular dimplesthat are provided in both opposing surfaces 52 and 54. Morespecifically, each dimple 62 in surface 52 is aligned with acorresponding dimple 62 in surface 54 as illustrated in FIGS. 7 and 8such that a rigid membrane or lamina 64 is defined between eachcorresponding pair of dimples 62. The combination of cooling effects andweight reduction is optimized when a ratio of dimple diameter D to itsdepth d (i.e., D/d) is in a range of 2 to 20, and when a ratio of anaxial thickness m of lamina 64 at dimple depth d to axial thickness T(i.e., m/T) is in a range of 0.1 to 0.3.

The present invention is not limited to use of circular dimples in oneor both of the rotor's opposing braking surfaces. For example, and withsimultaneous reference to FIGS. 9-10, a disc brake rotor in accordancewith another embodiment of the present invention is shown and isreferenced generally by numeral 70 in FIG. 9 where an axial end view ofthe rotor is illustrated. Rotor 70 includes an annular portion 80defining opposing braking surfaces 82 and 84, and radial edges 86 and 88where surfaces 82/84 and edges 86/88 traverse a periodic wave sharing acommon pattern and period as in the previously-described embodiments.Thermal radiation elements 90 can be coupled to one or both (as shown)of radial edges 86 and 88 and can be governed by the same thicknessratio as in the previously-described embodiments.

Rotor 70 additionally includes elongated dimples 92 in one or both (asshown) of opposing surfaces 82 and 84. When provided in both opposingsurfaces 82 and 84, each dimple 92 in surface 82 is aligned with acorresponding dimple 92 in surface 84 as illustrated in FIG. 10 suchthat a rigid membrane or lamina 94 is defined between each correspondingpair of dimples 92. The combination of cooling effects and weightreduction is optimized when a ratio of dimple width W to its depth d(i.e., W/d) is in a range of 2 to 20, and when a ratio of an axialthickness m of lamina 94 at dimple depth d to axial thickness T (i.e.,m/T) is in a range of 0.1 to 0.3.

As mentioned above, the inclusion of dimples in rotors of the presentinvention improves the rotor's convective and conductive coolingeffects. These effects will be explained with reference to FIG. 11 wherean isolated cross-sectional view of a dimpled region of rotorconstructed in accordance with the present invention is illustrated.While FIG. 11 depicts circular dimples 62 and corresponding lamina 64,it is to be understood that the principles to be described below alsoapply to elongate dimples. As air flow 100 moves over the brakingsurfaces 52/54, dimples 62 and the thin shared lamina 64 disrupt thelaminar part of air flow 100 to create a turbulent flow 102 inside ofdimples 62 to thereby enhance convective cooling. Lamina 64 alsoprovides a conductive thermal path 200 within the rotor such that theconducted heat is dissipated by turbulent flow 102.

Dimpled embodiments of the present invention can also be adapted toprovide enhanced radiative cooling. Referring now to FIG. 12, theexposed surfaces of dimples 62 are coated with a material 66 that has ahigh thermal emissivity values in a range of 0.3 to 0.99. Such materialscan include, but are not limited to, any high temperature black paintsor spray-on coatings under trade names such as Cerablak HTP, AcktarBlack Coatings, and Aremco HiE-Coat 840-MS. Material 66 can also be ablack anodized aluminum. The presence of material 66 enhances theradiative cooling effects indicated by wavy arrows 300.

The advantages of the present invention are numerous. The disc brakerotor of the present invention provides improved heat dissipation andcan include a variety of weight reducing features. The features of thepresent invention are readily incorporated into either perimeter orhub-mounted disc brake rotors to greatly improve their viability in avariety of wheeled vehicle applications.

Although the invention has been described relative to a specificembodiment thereof, there are numerous variations and modifications thatwill be readily apparent to those skilled in the art in light of theabove teachings. For example, through holes or slots can be provided inthe thermal radiation elements to achieve additional weight reductionand to reduce a rotor's internal high temperature stress due tothermal-expansion, if needed. It is therefore to be understood that,within the scope of the appended claims, the invention may be practicedother than as specifically described.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A disc brake rotor, comprising: an annularportion having a first surface and a second surface in opposition tosaid first surface, said annular portion having an axial thickness Tbetween said first surface and said second surface, said first surfaceand said second surface traversing a periodic wave wherein an innerradial edge of said annular portion traverses an inner periodic wave andan outer radial edge of said annular portion traverses an outer periodicwave, and wherein a pattern and a period are the same for said periodicwave, said inner periodic wave, and said outer periodic wave; andthermal radiation elements coupled to said inner radial edge betweenadjacent crests of said inner periodic wave and coupled to said outerradial edge between adjacent crests of said outer periodic wave.
 2. Adisc brake rotor as in claim 1, further comprising: first dimples insaid first surface; second dimples in said second surface; and each ofsaid first dimples being aligned with a corresponding one of said seconddimples wherein a lamina is defined there between.
 3. A disc brake rotoras in claim 2, wherein said first dimples and said second dimplescomprise circular dimples.
 4. A disc brake rotor as in claim 3, whereinsaid circular dimples have a diameter D and a depth d, wherein saidlamina has an axial thickness m at said depth d, wherein a ratio of D/dis in a range of 2 to 20, and wherein a ratio of m/T is in a range of0.1 to 0.3.
 5. A disc brake rotor as in claim 2, wherein said firstdimples and said second dimples comprise elongated dimples.
 6. A discbrake rotor as in claim 5, wherein said elongated dimples have a width Wand a depth d, wherein said lamina has an axial thickness m at saiddepth d, wherein a ratio of W/d is in a range of 2 to 20, and wherein aratio of m/T is in a range of 0.1 to 0.3.
 7. A disc brake rotor as inclaim 1, wherein at least one of said first surface and said secondsurface includes dimples.
 8. A disc brake rotor as in claim 7, furthercomprising a material coating surfaces of said dimples wherein saidmaterial has a thermal emissivity value in a range of 0.30 to 0.99.
 9. Adisc brake rotor as in claim 1, wherein said thermal radiation elementshave an axial thickness t, and wherein a ratio of t/T is in a range of0.1 to 0.3.
 10. A disc brake rotor, comprising: an annular portionhaving a first surface and a second surface in opposition to said firstsurface, said annular portion having an axial thickness T between saidfirst surface and said second surface, said first surface and saidsecond surface traversing a periodic wave wherein an inner radial edgeof said annular portion traverses an inner periodic wave and an outerradial edge of said annular portion traverses an outer periodic wave,and wherein a pattern and a period are the same for said periodic wave,said inner periodic wave, and said outer periodic wave; thermalradiation elements coupled to said inner radial edge between adjacentcrests of said inner periodic wave and coupled to said outer radial edgebetween adjacent crests of said outer periodic wave, said thermalradiation elements having an axial thickness t, and wherein a ratio oft/T is in a range of 0.1 to 0.3; and at least one of said first surfaceand said second surface includes dimples.
 11. A disc brake rotor as inclaim 10, wherein said dimples comprise: first dimples in said firstsurface; second dimples in said second surface; and each of said firstdimples being aligned with a corresponding one of said second dimpleswherein a lamina is defined there between.
 12. A disc brake rotor as inclaim 11, wherein said first dimples and said second dimples comprisecircular dimples.
 13. A disc brake rotor as in claim 12, wherein saidcircular dimples have a diameter D and a depth d, wherein said laminahas an axial thickness m at said depth d, wherein a ratio of W/d is in arange of 2 to 20, and wherein a ratio of m/T is in a range of 0.1 to0.3.
 14. A disc brake rotor as in claim 11, wherein said first dimplesand said second dimples comprise elongated dimples.
 15. A disc brakerotor as in claim 14, wherein said elongated dimples have a width W anda depth d, wherein said lamina has an axial thickness m at said depth d,wherein a ratio of D/d is in a range of 2 to 20, and wherein a ratio ofm/T is in a range of 0.1 to 0.3.
 16. A disc brake rotor as in claim 11,further comprising a material coating surfaces of said dimples whereinsaid material has a thermal emissivity value in a range of 0.30 to 0.99.